What are the best shock absorbers?

I have a 2002 Chevy Silverado 1500 LS, my shocks are on their last leg and I am looking for an upgrade. I drive about 75% highway, 25% off-road. I'm looking for something that can really improve my handling at high speeds on pavement, yet the durability to get a little dirty. Suggestions?

i LOOOOOVE my bilstiens, like a whole diferent truck, better handling/cornering and softer ride over bumps.

Do you have the 5100 series from Bilstein, or which?

I was also wondering if it was better to have all four shocks the same, or if I were to put two leveling shocks (from Bilstein) in the front and two heavy duty shocks in the back for towing?
I'm looking for superior handling and decent off-roading, and maybe the ability to put more weight in the bed of the truck.